Aroma diffuser



FIG. 1 is a perspective view of the design for an aroma diffuser;

FIG. 2 is a front view of the design;

FIG. 3 is a rear view of the design;

FIG. 4 is a right side view of the design;

FIG. 5 is a left side view of the design;

FIG. 6 is a top view of the design; and,

FIG. 7 is a bottom view of the design.

The broken lines shown in the drawings are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for an aroma diffuser, as shown and described. 